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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    //求出1-1/2+1/3-.....-1/100
    var sel = 0
    for(var i = 1; i <= 100; i++){
        if(i % 2 !== 0){ //求出分母为奇数的值，进行加法运算
            sel = sel + 1 / i
        }else if(i % 2 === 0){ //求出分母为偶数的值，进行减法运算
            sel = sel - 1 / i 
        }
    }
    console.log(sel)
</script>
</html>